From 9dab3c51fd5e18b18838e0da4ee20f313d25ba43 Mon Sep 17 00:00:00 2001
From: OKURA Masafumi <masafumi.o1988@gmail.com>
Date: Mon, 6 Apr 2026 18:34:36 +0900
Subject: [DOC] Mention `Hash#default_proc=` affects Proc object from
 `Hash#to_proc`

```ruby
h = {foo: 0, bar: 1, baz: 2}
proc = h.to_proc
proc.call(:nosuch) # => nil
h.default_proc = proc {'wow!'} # This affects `proc` immediately
proc.call(:nosuch) # => 'wow!'
```

This behavior is a bit of surprise to me, and I could not find
any mention to this behavior in current doc.
---
 hash.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hash.c b/hash.c
index 773df7e78d..79dbd5d8e9 100644
--- a/hash.c
+++ b/hash.c
@@ -5012,6 +5012,8 @@ hash_proc_call(RB_BLOCK_CALL_FUNC_ARGLIST(key, hash))
  *    proc.call(:foo) # => 0
  *    proc.call(:bar) # => 1
  *    proc.call(:nosuch) # => nil
+ *    h.default_proc = proc { |hash, key| "Missing key: #{key}" } # This affect the existing proc object
+ *    proc.call(:nosuch) # => "Missing key: #{nosuch}"
  *
  *  Related: see {Methods for Converting}[rdoc-ref:Hash@Methods+for+Converting].
  */
-- 
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